An inchworm actuator has been known as a compact precise positioning mechanism. For example, Patent Document 1 discloses an inchworm actuator in which a movable body which moves on a guide includes three piezoelectric elements which expand upon receipt of electric energy. In this inchworm actuator, the movable body is moved along the guide by inchworm drive, i.e., by alternately repeating expansion and contraction operations of a feed piezoelectric element and clamping and unclamping operations of the two anchoring piezoelectric elements.
However, the above-described inchworm actuator has the problem that since the feed piezoelectric element is unclamped when no electricity is supplied to the two anchoring piezoelectric elements, the position of the movable body on the guide cannot be maintained. Therefore, the conventional inchworm actuator is inconvenient for use as a positioning mechanism. In view of this drawback, below-listed Patent Documents 2 and 3, for example, disclose inchworm actuators which can maintain the position of a movable body without the need for electric power.
Specifically, below-listed Patent Document 2 discloses an inchworm actuator which includes a link mechanism which brings clamp blocks into a clamping state so as to fix the position of a movable body when an anchoring piezoelectric element for the movable body contracts (i.e., when no electricity is supplied to the anchoring piezoelectric element). Below-listed Patent Document 3 discloses an inchworm actuator which includes a permanent magnet provided on a movable body and a magnetic attracting member provided on a base along which the movable body moves. The movable body is magnetically attracted and fixed to the base whereby the position of the movable body is maintained.